Hydrogenolysis of rice husk protolignin. II

It has been established that the partial hydrogenolysis of rice husk protolignin (RHP) takes place at a temperature of 180°C and an initial hydrogen pressure of 10 atm in an alkaline medium. Conditions have been selected under which the greatest yield of low-molecular-weight products (91% on the Komarov lignin) is obtained: hydrogenolysis in an alkaline medium in the presence of an anthraquinone (AQ) catalyst. The addition of AQ increases the yield of low-molecular-weight products by a factor of 1.8. Semiempirical formulas have been derived for incompletely hydrolyzed lignin residues. A study of the molecular-weight distribution of these lignins has shown that they are polydisperse. It has been established that in the process of hydrogenolysis AQ promotes the demethoxylation of structural units with syringyl nuclei.